Strip thickness measuring device for use in a rolling mill and like apparatus



June 23, 1970 D, sTONE 3,516,273

STRIP THICKNESS MEASURING DEVICE FOR USE IN A ROLLING MILL AND LIKEAPPARATUS 2 Sheets-Sheet 1 Filed Aug. 2, 1967 INVENTOR. MOAW/S 0. STONEJune 23, 1970 3,516,273 ING MILL M- .D. STONE STRIP THICKNESS MEASURINGDEVICE FOR USE IN A ROLL AND LIKE APPARATUS 2 Sheets-Sheet 2 Filed Aug.2. 1967 MWN INVENTOR. Q E Maw/s 0. are/v5 ATTOR/VEH United States Patent3,516,273 STRIP THICKNESS MEASURING DEVICE FOR USE IN A ROLLING MILL ANDLIKE APPARATUS Morris Denor Stone, Pittsburgh, Pa., assignor to UnitedEngineering and Foundry Company, Pittsburgh, Pa., a corporation ofPennsylvania Filed Aug. 2, 1967, Ser. No. 657,870 Claims priority,application Great Britain, Aug. 16, 1966, 36,664/66 Int. Cl. B21b 37/10US. CI. 7221 6 Claims ABSTRACT OF THE DISCLOSURE A strip thicknessmeasuring device for use in a rolling mill which is provided withcustomary roll balance cylinder assemblies that urge the rolls apart.The measuring device is built into the roll balance cylinder assembliesand measures the displacement of the plungers of the roll balancecylinder assemblies, which displacement corresponds to the actualseparation of the rolls which defines the thickness of the strip.

The present invention relates to a strip thickness measuring deviceadapted to measure the thickness of the material as it passes between apair of thickness reducing elements, such as the cooperative rolls of arolling mill or calender.

More particularly, the present invention relates to a materialprocessing apparatus comprising at least a pair of roll assemblies,means arranged between the roll as-' semblies for continuously urgingsaid roll assemblies apart to establish an initial distance between therolls and which means is responsive to change in distance between therolls, said roll assembly urging means including a means for continuallymeasuring and producing a signal representing a change in distancebetween the pair of roll assemblies, means for receiving said signal andfor producing a material thickness error signal representing thedifference between the actual distance and the initial distance betweensaid pair of rolls.

In one form, the present invention provides in a rolling mill a firstpiston cylinder assembly for applying a pressure in a direction opposingthe rolling load developed between the pair of reducing rolls of themill, said pressure being at all times equal to and greater than therolling load, a second piston cylinder assembly arranged between themill rolls for urging the rolls apart against said pressure and includesmeans for measuring the displacement of piston of said second pistoncylinder assembly and producing a signal representing said displacement,a control system for receiving said signal and comparing it with asignal representing the desired distance between the mill rolls, saidsystem adapted to produce a signal representing the difference betweensaid two signals, and effect a change in the pressure of said firstpiston cylinder assembly so as to change the position of the rolls withrespect to each other, in order that the difference between said signalsis reduced substantially to zero.

In the art of producing strip-like material, for example metallic stripin a rolling mill, due to the fact that the components of the millcontinuously stretch in varying amounts under an ever-changing rollingforce, it has heretofore been extremely difiicult to obtain longitudinalconsistency in the gauge of the material. While a number of methods andapparatuses have been proposed and tried for compensating for theelastic stretch of the mill, all of these possess certain seriouslimitations. For example, the invention of U8. Pat. No. 2,680,978 whichissued on June 15, 1954 entitled Production of Sheet and Strip is foundobjectionable in that a substantial delay is experienced from the timethe correction signal is produced until the correction is made. Thisdelay is due mainly to the inertia of the screwdown, and results in theproduction of substantial off-gauge material. British Pat. No. 955,164dated Apr. 15, 1964 entitled Improvements in and Relating to RollingMills is a more recent attempt to solve the problem. This suggestion isobjectionable from the standpoint that the correction signal onlycompensates for a small part of the mill stretch and, as a result, atruly accurate gauge cannot be reached.

The present invention provides a mechanism for actually measuring thedistance between the processing rolls of a processing apparatus, such asa calender or mill, in a way wherein the employment thereof requiresvery little change in the construction of the apparatus.

One form of the present invention is illustrated in the followingdrawings, of which:

FIG. 1 is a diagrammatical view of a 4-high mill incorporating thefeatures of the present invention;

FIG. 2 is a schematic view of two cooperative work roll balance cylinderassemblies shown in conjunction with the gauge control system foroperating the mill;

FIG. 3 is an enlarged partial elevational view of the balance cylinderassembly and strip thickness measuring device shown in FIG. 1;

FIG. 4 is a second embodiment of a balance cylinder assembly stripthickness measuring device; and

FIG. 5 is a comparison of the mill spring curves of a conventional milland one built in accordance with the present invention.

With reference to the FIG. 1, there is illustrated one of the housingsof a 4-high mill, which includes a window 11 into which there isreceived backup chocks 12 for rotatably supporting backup rolls 13, thebackup chocks being formed in their adjacent sides With openings 15 forthe receipt of work roll chocks 16 which rotatably support the Workrolls 17. The rolls 17 are urged apart by a pair of piston cylinderassemblies 18 for each pair of chocks, i.e. a pair for each roll end,the construction details of which will be more fully explained later on.

Between the backup chocks there are provided the usual backup balancecylinder assemblies 19 which separate the backup chocks and assure thatthe upper chocks are held against the mill screw 20 which is received ina nut 21 mounted in the housing 10. The screw is rotated in the usualmanner by a worm-wheel motor unit, not shown. At the bottom of the mill,the lower backup chock 12 is engaged by the piston of the pistoncylinder assembly 22. As FIG. 2 shows, the piston of the cylinderassembly 22 is connected to a servovalve 23, the hydraulic side of thevalve being in turn connected to a pump 24 driven by an electrical motor25. It will be appreciated that the components of the other mill housingare identical to the one just described so that a description thereof isnot deemed necessary.

At this point, reference is made to FIG. 3, which illustrates anenlarged drawing of one of the balance cylinder assemblies providedbetween a pair of work roll chocks 16 of the mill illustrated in FIG. 1,As shown, the upper work roll chock 16 is urged apart from the lower one16 by a plunger 26 of one of the four balance cylinder assemblies 18. Asshown, the lower work roll chock 16, in the usual way, is provided witha recess 27 into which there is received the cylinder 28 of one of thebalance cylinder assemblies 18.

The plunger 26 of the cylinder assembly is acted on by pressurized fluidfrom the passageway 31 from a source, not shown. The plunger 26 is madehollow and into the center thereof is mounted an electrical displacement measuring device 32. The outer portion of the device comprises anarmature winding 33 into which is received in reciprocatory fashion anarmature 34, the top of the armature being connected to the top of theplunger 26 and moves with it. The armature winding 33 receives currentfrom electrical lines L1 and L2. The change in voltage which is causedby the armatures movement will be measured by means now to be described.In this construction the exposed portion of the plunger 26 is employedas a representation of the thickness of the material passing between thework rolls 17, which is converted into an accurate proportionalelectrical signal by the displacement measuring device 32.

A second embodiment of the displacement indicating device is illustratedin FIG. 4 where, it will be noted, the balance cylinder 37 is made of anon-magnetic material, whereas the cylinder plunger 38 is preferablymade up of a magnetic material, such as brass or the like. A transformercoil 39 is wound in the cylinder 37 to produce a flux field throughwhich the plunger 38 passes, thereby producing an electrical signal thatwill vary with the particular position of the plunger relative to thecoil 39. As noted above, the plunger represents the desired gap distancebetween the work rolls 17 which, for all practical purposes, representsthe gauge of the material in the bite of the rolls.

Turning now to the control system represented in FIG. 2, there isillustrated for simplicity only the displacement indicating devices 32of two cooperative balance cylinder assemblies 18. As indicated, thedisplacement indicating devices 32 are arranged in series to form acombined resistance 42a in one leg of a Wheatstone bridge circuit 41which is connected in a conventional manner to a power source, notshown, by lines L3 and L4. By placing the pair of indicating devices 32in series in the one leg, any tendency of the work roll chocks 16 torotate or tilt is compensated for. Resistors 42b, 42c and 42d, one ofwhich is selectively variable to take care of mill conditions, arecombined with the resistance 42a to form the other legs of the bridgecircuit which has a voltage sensing device 422 from which is deliveredvoltage to an amplifier and then through line L5 to the servovalve 23.Operation of the bridge circuit is such that the resistance 42a becomesa variable since, as previously indicated, it is the sum of theresistances of the devices 32. These variations create an imbalancedcondition resulting upon the displacement of the chocks 16 and representan off-gauge condition. The imbalanced condition which may be plus orminus, is balanced by employing the output voltage of the device 42e asa signal to operate the servovalve 23 which will elfect operation of thepiston cylinder assembly 22 to change its pressure pursuant to thissignal. This will eflect a change in the gap until the plunger 26 of thecylinder 28 has been moved suflicient to balance the bridge circuit.

In a particular construction, the plunger of the balance cylinderassembly may have a movement of 4 inches, wherein the device 32 or coil39 will be sensitive to a change in movement of the order of .0001 inch.

It should be noted that one of the advantages derived from the presentinvention is that the devices 32 can be built conveniently into thechocks of an existing mill, thus requiring very little initial expense.A second significant advantage is that the present invention providesfor the displacement indicating devices being mounted internally in thebalance cylinder assemblies 18, thereby protecting the devices from theoutside environment of the mill.

It will be appreciated by those skilled in the art that while ahydraulic form of adjusting the rolls has been shown, various otherconstructions can be employed for changing the position of the workrolls, the primary thought being that the change will be made assimultaneously as possible from the time that an error is detected inthe displacement of the balance cylinders of the balance cylinderassembly.

A representation of the eifectiveness of the present invention is givenin FIG. 5 where a comparison is made of the mill spring curves of aconventional mill and a mill incorporating the present invention. Asshown in FIG. 5, the mill spring curve for the conventional mill withrespect to the point 0 and o and the lines drawn perpendicular to thebase line t forms a substantial angle. In the conventional mill At i.e.the change in material thickness due to mill spring resulting from achange in rolling load P is substantial. For example, a variation inincoming strip thickness of .0050 inch, i.e. where t t =At will resultin a variation of mill spring of At which in turn will result in anoutgoing strip thickness variation of .0040 inch.

In the spring curve of a mill incorporating the present invention thesame legends have been used in which the effective mill modulus is500x10 lbs./in. in comparison with 20x10 lbs./in. in a conventionalmill. This substantial improvement in the mill modulus is seen in thecharacteristic of the slope of the mill spring curve shown in FIG. 5. Inthe improved mill the curve is substantially vertical to the base line tand the difierence between point 0 and point 0' on the mill spring curveis very slight. Thus, for a variation in incoming strip thickness of.0050 inch a variation in outgoing gauge will be .0002 inch as to thechange in gauge resulting from the mill stretch. The variation is,therefore, reduced to only 5% of what would usually occur and isequivalent to an improvement of v In accordance with the provisions ofthe patent statutes, I have explained the principle and operation of myinvention and have illustrated and described what I consider torepresent the best embodiment thereof. However, I desire to have itunderstood that within the scope of the appended claims, the inventionmay be practiced otherwise than as specifically illustrated anddescribed.

I claim:

1. In an apparatus for processing elongated material, which apparatuscomprises a housing, first and second parallelly disposed cooperativerolls arranged to form a pass opening into which the material to beprocessed is fed, the ends of said rolls being rotatably mounted inbearing chock assemblies received in said housing, means for adjustingsaid first roll relative to the second roll to vary the pass opening,pressure exerting means including a displaceable plunger arrangedbetween opposed bearing chock assemblies of said rolls for continuouslyurging said rolls apart and before processing commences to establish aninitial pass opening between said rolls,

the improvement comprises means associated with said pressure exertingmeans, responsive to a change in the displacement of said plungers ofsaid pressure means in a direction corresponding to the separation ofthe rolls and a change in the pass opening, means associated With themeans responsive to a change in the displacement of said plunger adaptedto produce a signal representative of the amount of displacement of saidplunger, and a change in said pass opening.

2. In an apparatus according to claim 1, in which said pressure exertingmeans comprises a first pair of piston cylinder assemblies and saidplungers constituting the plungers of these assemblies, said means foradjusting said first roll comprising a second pair of piston cylinderassemblies arranged in said housing and adapted to apply a pressure in adirection to oppose the separation of said roll, said pressure of saidsecond piston cylinder assemblies being equal to or greater than theseparating force developed between said pair of rolls, means forreceiving said signal and adapted to compare said signal with a secondsignal representative of the desired distance between said rolls, meansfor producing a third signal representative of the difierence betweensaid first and second signals, means for receiving said third signal andadapted to vary the pressure in said second piston cylinder assembliesso as to move said first roll towards and away from said second rolluntil the difference between said first and second signals issubstantially zero.

3. In an apparatus according to claim 1, including a power driven screwmeans carried by said housing for adjusting said second roll relative tosaid first roll to initially establish the desired pass opening.

4. In an apparatus according to claim 1, wherein for each processingroll there is provided a backup roll, bearing chock assemblies for saidbackup rolls received in said housing, said pressure exerting meanscomprising a pair of piston cylinder assemblies for each pair of opposedbearing chock assemblies of said processing rolls, and wherein saidmeans for producing a signal representative of the amount ofdisplacement of said plungers producing a signal of the sum of thedisplacement of the plungers for each pair of said piston cylinderassemblies, means for receiving said signal and adapted to compare saidsignal with a second signal representative of the desired distancebetween said rolls, means for producing a third signal representative ofthe diiference between said first and second signals, means forreceiving said third signal and adapted to vary the pressure in saidsecond piston cylinder assemblies so as to move said first roll towardsand away from said second roll until the ditference between said firstand second signals is substantially zero.

5. In an apparatus according to claim 1, wherein said pressure exertingmeans comprises piston cylinder assemblies in which said plungers act asthe pistons of said assemblies, said plungers having hollow interiorportions, armature connected to the plungers and movable therewithrelative to said cylinders, said armatures moving into armature windingssecured to said cylinders, and means for supplying electric current tosaid armature windings.

6. In an apparatus according to claim 1, in which said pressure exertingmeans comprises piston cylinder assemblies, said cylinders of saidassemblies being formed of non-magnetic material, said plungerscomprising the pistons of said assemblies and being formed of magneticmaterial, transformer coils wound in said cylinders adapted to produce aflux field through which said plungers pass, thereby to produce anelectrical signal that will vary with the particular position of theplunger relative to the transformer coil.

References Cited UNITED STATES PATENTS 3,208,251 9/1965 Hulls, et a1.7216 3,286,495 11/1966 Diolot 728 3,326,028 6/1967 Kajiwara 72-240FOREIGN PATENTS 1,027,704 4/1966 Great Britain.

LOWELL A. LARSON, Primary Examiner US. Cl. X.R.

